#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main() {
    float r1, r2;
    float zhi = 0;
    scanf("%f %f", &r1, &r2);
    zhi = 1.0 / (1.0 / r1 + 1.0 / r2);
    printf("%f", zhi);

    return 0;
}